This "dead marsh" sits among the largest sand dunes in the world, a forest frozen in time.

A sulfuric martian landscape that looks far better than it smells.

An underground city of salt.

A Romanian church built from one single oak.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

A whimsical bridge adorned with decorative dragons.

One of Ireland's most infamous prisons for rebels including men, women and children.

The biggest and deepest Cold War bunker open to the public can be found in southeast England.

This elegant arc of a waterfall marks a religious turning point.

The 1936 Summer Olympics site is a crumbling remnant of sportsmanship and a history its host country would like to forget.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

The most famous location in China was home to whole dynasties worth of imperial rulers.

The Guardian of Tallinn.

This medieval Estonian tower provides access to a series of tunnels that have been home to soldiers, punks, and fine art.

Fascinating town where normal life interfaces with the occult.

Abstract dinosaur models in London.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This complex of vertically-excavated Buddhist, Jain, and Hindu monolithic temples in India's Maharashtra providence illustrates a spirit of tolerance characteristic of ancient India.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

Real bones which are said to have belonged to a Polish dragon.

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

Copenhagen's celebrated theme park and gardens.

Human-made caves excavated to hide a secret society of wealthy pagans.

Three columns of volcanic rock shoot out of the ocean.